The present invention relates to a key switch device which performs a switching action while guiding a vertical movement of a key top by means of a pair of link members, a keyboard provided with the key switch device, and an electronic device provided with the keyboard. More particularly, the present invention relates to a key switch device which does not need a rubber spring generally used in a conventional key switch device and a complicated key top urging mechanism, and which can realize a key operation with a fine click touch in operating a key top and freely design the click touch, so that a constant depression characteristic of the key top can be maintained over a long term and furthermore the cost of the whole key switch device can be reduced, and a keyboard provided with the key switch device and an electronic device provided with the keyboard.
In association with the reduction in size, thickness, and others of a notebook-size personal computer which is one of electronic devices instruments, conventionally, there have been proposed various types of key switch devices to be used for a keyboard provided in the computer. This type of key switch device generally uses a rubber spring which urges a key top upward to hold the key top in a non-pressed position, whereas the rubber spring buckles with a click when the key top is pressed down, then performing a switching operation, and returns the key top to the non-pressed position after the switching operation.
The rubber spring is usually made of silicone rubber, EPDM rubber, etc., which is in general high in cost and the work of properly mounting the rubber spring while positioning in place in the key switch device. In the case where the rubber spring is used, the switching characteristic of the key switch device largely depend on the property of the rubber spring. It would therefore become difficult to freely change the switching characteristic of the key switch device.
In view of the above circumstances, many proposals to realize a key switch device without use of a rubber spring have been presented. For instance, Japanese patent unexamined publication No. 10-172380 discloses a key switch device in which a pair of first and second links are movably arranged between a hook of a key top and a hook of a base mold to guide the key top in a vertical direction, and a rubber sheet is stretched over between joint portions of the links.
In this key switch device, a circular projection formed on the underside of the key top is in close contact with the rubber sheet at the time of non-depression to hold the key top in a non-pressed state. When the key top is depressed, the key top presses the rubber sheet downward through the circular projection with increasing a tension of the rubber sheet so that the rubber sheet projects downward through a through hole, thereby switching, with a click, a switching area of a membrane sheet supported on a bottom plate. It is to be noted that, upon cancellation of the depression of the key top, the key top is moved upward by an elastic force of the rubber sheet to the original, non-pressed position.
The key switch device disclosed in the above-mentioned Japanese patent unexamined publication No. 10-172380, using no rubber spring, is not influenced by the size of a rubber spring and therefore can achieve an increase in designing freeness of the key switch device.
Although the above key switch device does not use a generally used rubber spring, however, the rubber sheet simply substitutes for the rubber spring and the rubber sheet is essential for the structure of the key switch device. It is therefore still insufficient in cost reduction of the whole key switch device. Furthermore, there is a problem that the work of stretching the rubber sheet over between the joints of the pair of links would complicate the work of assembling the key switch device. The key switch device also could perform a switching operation with a click touch when the key top is depressed; however, it is very difficult to freely design this click touch.
Furthermore, there has conventionally been proposed another key switch device configured so as to urge a key top upward through an elastic resinous member instead of the rubber spring and the rubber sheet. This elastic resinous member can be formed integrally with a resinous member constituting the key switch device and therefore it is effective in cost. If the key switch device is used for a long term, however, the elastic member may wear and a creep phenomenon may occur due to the stress repeatedly exerted on the elastic member, resulting in plastic deformation. When the elastic member wears and the plastic deformation occurs in the elastic member, the depression characteristic of the key top would be changed, deteriorating the key operability. When the wear and plastic deformation of the elastic member further advance, the elastic member could not elastically support any longer the vertical movement of the key top and, in some cases, the key switch device could not operate due to breakage or the like of the elastic member.
The present invention has been made to overcome the above problems and has an object to provide a key top device which can realize a key operation with a fine click touch during operation of a key top without needing a rubber spring generally used in a key switch device and a complicated key top urging mechanism, allow free design of the click touch, hold a constant depression characteristic of the key top over a long term, and achieve reduction in cost of the whole key switch device, and a key board provided with the key switch device and an electronic device provided with the keyboard.
(1) To achieve the purpose, the key switch device according to the first invention is a key switch device including a key top and a pair of a first and a second link members movably disposed under the key top, for performing switching of a switching section while guiding a vertical movement of the key top by the first and second link members, characterized by including: a first cam portion formed in the first link member; a second cam portion formed in the second link member and disposed facing the first cam portion; a cantilever member formed in a cantilever beam shape extending from the first link member or the second link member to support at least one of the first cam portion and the second cam portion; and an urging member for elastically urging the cantilever member in which one of the cam portions is formed in a direction to bring the first cam portion and the second cam portion into contact with each other.
The key switch device according to the first invention is characterized in that the first or second link member formed with the cantilever member is provided with a placing part for placing the urging member.
Furthermore, the key switch device according to the first invention is characterized in that the urging member is constructed of a torsion spring including a first arm which comes into contact with the cantilever member and a second arm facing the first arm, the placing part includes a first holding part for holding the first arm and a second holding part for holding the second arm.
The key switch device according to the first invention is characterized in that the first holding part movably holds the first arm and the second holding part fixedly holds the second arm.
In the key switch device according to the first invention having the above structure, one of the first cam portion of the first link member and the second cam portion of the second link member is supported by the cantilever member extending like a cantilever beam from the first or second link member and the urging member urges the cantilever member in the direction to bring the first and second cam portions into contact with each other. By the contact state of the first cam portion of the first link member and the second cam portion of the second link member and the cooperative operation of the urging member which urges the cantilever member, the key top is urged upward and held in the non-depressed position and the key top can be returned to the non-depressed position upon cancellation of depression. Accordingly, the key switch device can be constructed without use of a rubber spring and a complicated urging mechanism, thus achieving a cost reduction. The urging member urges the cantilever member, so that the first and second cam portions are constantly held in contact with each other with the contact position varying in response to the vertical movement of the key top. By changing the shapes of the first and second cam portions as needed, therefore, it is possible to freely design the click touch which occurs during the key operation.
Furthermore, the cantilever member is elastically urged by the urging member so that one of the first and second cam portions supported on the cantilever member is held in contact with the other cam portion. The elastic force to bring the first and second cam portions into contact with each other may be produced by the urging member. Accordingly, the cantilever member is not requested to have the elastic force. Thus, the cantilever member can be made of a resinous material at low cost and to be relatively flexible. Consequently, there is little possibility that creep occurs in the cantilever member even when the switching operation is performed for a long term, and the switching operation can be ensured stably over a long term.
Furthermore, the placing part for placing the urging member is provided in the first or second link member, so that the urging member can integrally be mounted in the first or second link member, thus achieving a size reduction of the whole key switch device.
The torsion spring having the first and second arm portions is used as the urging member and the first and second arm portions are held respectively by the first and second holding parts of the placing part to hold the first and second arm portions which provide the urging force to each other in the torsion spring. This simple structure makes it possible to efficiently transmit the urging force produced between the arm portions to the cantilever member.
Moreover, the first arm portion is movably held in the first holding part and the second arm portion fixedly held in the second holding part, so that the urging force generated by the torsion spring is transmitted from the first arm portion being in contact with the cantilever member to the cantilever member. At this time, the first arm portion being movably held in the first holding part, during depression of the key top, the first arm portion is allowed to flexibly move in the first holding part in response to reactive force resulting from the contact force occurring between the first and second cam portions, while constantly holding the first and second cam portions in a contact relation.
(2) The key switch device according to the second invention is a key switch device including a key top and a pair of a first and a second link members movably disposed under the key top, for performing switching of a switching section while guiding a vertical movement of the key top by the first and second link members, characterized by including: a first cam portion formed in the first link member; a second cam portion formed in the second link member and disposed facing the first cam portion; a first cantilever member formed in a cantilever beam shape extending from the first link member to support the first cam portion; a second cantilever member formed in a cantilever beam shape extending from the second link member to support the second cam portion; a first urging member for elastically urging the first cantilever member in a direction to bring the first cam portion and the second cam portion into contact with each other; and a second urging member for elastically urging the second cantilever member in a direction to bring the first cam portion and the second cam portion into contact with each other.
The key switch device according to the second invention is characterized in that the first and second link members are provided with placing parts for placing the urging members respectively.
The key switch device according to the second invention is characterized in that the urging member is constructed of a torsion spring including a first arm which comes into contact with the cantilever member and a second arm facing the first arm, the placing part includes a first holding part for holding the first arm and a second holding part for holding the second arm.
The key switch device according to the second invention is characterized in that the first holding part movably holds the first arm and the second holding part fixedly holds the second arm.
In the key switch device according to the second invention, the first cantilever member supporting the first cam portion of the first link member is urged by the first urging member and the second cantilever member supporting the second cam portion of the second link member is urged by the second urging member, respectively, in a direction to bring the first and second cam portions into contact with each other. Accordingly, by the contact state of the first and second cam portions and the cooperative operation of the first and second urging members which urge the first and second cantilever members respectively, the key top is urged upward and held in the non-depressed position and the key top can be returned to the non-depressed position upon cancellation of depression. Accordingly, the key switch device can be constructed without use of a rubber spring and a complicated urging mechanism, thus achieving a cost reduction. The first and second urging members urge the first and second cantilever members, so that the first and second cam portions are constantly held in contact with each other with the contact position varying in response to the vertical movement of the key top. By changing the shapes of the first and second cam portions as needed, therefore, it is possible to freely design the click touch which occurs during the key operation.
Furthermore, the first and second cantilever members are elastically urged by the first and second urging members respectively so that the first and second cam portions supported on the cantilever members are brought into contact with each other. The elastic force to bring the first and second cam portions into contact with each other may be produced by the first and second urging members. Accordingly, the first and second cantilever members are not requested to have the elastic force. Thus, each cantilever member can be made of a resinous material at low cost and to be relatively flexible. Consequently, there is little possibility that creep occurs in each cantilever member even when the switching operation is performed for a long term, and the switching operation can be ensured stably over a long term.
Furthermore, the placing parts for placing the urging members are provided in the first and second link members, so that the urging members can integrally be mounted in the first and second link members, thus achieving a size reduction of the whole key switch device.
The simple structure that the torsion spring having the first and second arm portions is used as the urging member, the first and second arm portions are held respectively by the first and second holding parts of the placing part to hold the first and second arm portions which provide the urging force to each other in the torsion spring. Accordingly, the urging force produced between the arm portions can be transmitted efficiently to the cantilever member.
Moreover, the first arm portion is movably held in the first holding part and the second arm portion fixedly held in the second holding part, so that the urging force generated by the torsion spring is transmitted to the cantilever member from the first arm portion being in contact with the cantilever member. At this time, the first arm portion being movably held in the first holding part, during depression of the key top, the first arm portion flexibly moves in the first holding part in response to reactive force resulting from the contact force occurring between the first and second cam portions, while constantly holding the first and second cam portions in a contact relation.
(3) The key switch device according to the third invention is a key switch device including a key top and a pair of a first and a second link members movably disposed under the key top, for performing switching of a switching section while guiding a vertical movement of the key top by the first and second link members, characterized by including: a first cam portion formed in the first link member; a second cam portion formed in the second link member and disposed facing the first cam portion; a cantilever member formed in a cantilever beam shape extending from the first link member or the second link member to support at least one of the first cam portion and the second cam portion; and an urging member for elastically urging the cantilever member in which one of the cam portions is formed in a direction to bring the first cam portion and the second cam portion into contact with each other, wherein the first cam portion and the second cam portion are brought into contact with each other at contact portions, the first cam portion and the second cam portion each have a shape to cause the point of action of the urging force of the urging member acting on the contact portions to shift to a predetermined fixed point side of the urging member in association with a repeated switching operation.
The key switch device according to the third invention is characterized in that the first or second link member formed with the cantilever member is provided with a placing part for placing the urging member.
The key switch device according to the third invention is characterized in that the urging member is constructed of a torsion spring including a first arm which comes into contact with the cantilever member and a second arm facing the first arm, the placing part includes a first holding part for holding the first arm and a second holding part for holding the second arm.
The key switch device according to the third invention is characterized in that the first holding part movably holds the first arm and the second holding part fixedly holds the second arm.
The key switch device according to the third invention is characterized in that one of the cam portions supported by the cantilever member is formed with a first cam surface parallel to the first arm, the other cam portion of the first cam portion and the second cam portion is formed with a second cam surface which is brought into contact with the first cam surface in the contact portions at an acute angle in plan view and has a slanted surface, and a clearance is provided between the first cam surface and the slanted surface to open from the contact portions toward the fixed point side of the urging member.
In the key switch device according to the third invention, one of the first cam portion of the first link member and the second cam portion of the second link member is supported by the cantilever member extending like a cantilever beam from the first or second link member and the urging member urges the cantilever member in the direction to bring the first and second cam portions into contact with each other. By the contact state of the first cam portion of the first link member and the second cam portion of the second link member and the cooperative operation of the urging member which urges the cantilever member, the key top is urged upward and held in the non-depressed position and the key top can be returned to the non-depressed position upon cancellation of depression. Accordingly, the key switch device can be constructed without use of a rubber spring and a complicated urging mechanism, thus achieving a cost reduction. The urging member urges the cantilever member, so that the first and second cam portions are constantly held in contact with each other with the contact position varying in response to the vertical movement of the key top. By changing the shapes of the first and second cam portions as needed, therefore, it is possible to freely design the click touch which occurs during the key operation.
Furthermore, the cantilever member is elastically urged by the urging member so that one of the first and second cam portions supported on the cantilever member is brought into contact with the other cam portion. The elastic force to bring the first and second cam portions into contact with each other is produced based on the elastic force of the cantilever member and the elastic force of the urging member.
At this time, the contact portions of the first and second cam portions may wear due to the repeated switching operation in the switching section based on the depression operation of the key top, which reduces the initial urging force which is exerted on the cantilever member through the urging member. The first and second cam portions each have the shape to cause the point of action of the urging force acting on the contact portions of the first and second cam portions to shift to a predetermined fixed point side of the urging member while the switching operation is repeatedly performed in the switching section. In the case where the contact portions wear, the point of action of the urging force comes close to the fixed point side of the urging member, increasing the urging force to be exerted on the cantilever member through the urging member. Thus, the reduction in the initial urging force of the urging member due to wear of the contact portions of the first and second cam portions is cancelled out by an increment of the increased urging force when the point of action of the urging force in the contact portions comes close to the fixed point side of the urging member. Consequently, even if the switching operation is repeatedly performed for a long term, the depression characteristic of the key top can be surely prevented from being largely changed and can be stabilized. The switching operation can be ensured stably over a long term.
In the case where the elastic force of the cantilever member is reduced due to the repeated switching operation, similarly, the action point of the urging force of the urging member in the contact portions of the first and second cam portions comes close to the fixed point side of the urging member as mentioned above, which increases the urging force which is exerted on the cantilever member through the urging member. Accordingly, the increased urging force can compensate the reduction in the elastic force of the cantilever member. This also makes it possible to stabilize the depression characteristic of the key top.
Furthermore, the placing part for placing the urging member is provided in the first or second link member, so that the urging member can integrally be mounted in the first or second link member, thus achieving a size reduction of the whole key switch device.
The simple structure that the torsion spring having the first and second arm portions is used as the urging member, the first and second arm portions are held respectively by the first and second holding parts of the placing part to hold the first and second arm portions which provide the urging force to each other in the torsion spring. Accordingly, the urging force produced between the arm portions can be transmitted efficiently to the cantilever member.
Moreover, the first arm portion is movably held in the first holding part and the second arm portion fixedly held in the second holding part, so that the urging force generated in the torsion spring is transmitted to the cantilever member from the first arm portion being in contact with the cantilever member. At this time, the first arm portion being movably held in the first holding part, during the depression operation of the key top, the first arm portion flexibly moves in the first holding part in response to reactive force resulting from the contact force occurring between the first and second cam portions, while constantly holding the first and second cam portions in a contact relation.
Furthermore, one of the cam portions is formed with the first cam surface and the other is formed, at the contact portion with respect to the first cam surface, with the second cam surface which has a slanted surface and comes into contact with the first cam surface at an acute angle thereto in plan view. The clearance is provided to be open toward the fixed point side of the urging member from the contact portion between the first cam surface and the slanted surface. In the case where the acutely-angled second cam surface wears due to the repeated switching operation at the switching section in response to the depression operation of the key top, the second cam surface will wear in a direction that the clearance being between the first cam surface and the slanted surface is gradually closed toward the fixed point side of the urging member from the contact portions. As a result, the action point of the urging force of the urging member comes close to the fixed point side of the urging member, which increases the urging force to be exerted on the cantilever member through the urging member. Thus, even when the initial urging force of the urging member is reduced due to the wear of the second cam surface, the reduction in the initial urging force is compensated by an increment of the increased urging force when the action point of the urging force in the contact portions of the first and second cam portions comes close to the fixed point side of the urging member. Consequently, even if the switching operation is repeatedly performed for a long term, the depression characteristic of the key top can be prevented from being largely changed and can be stabilized, ensuring a stable switching operation over a long term.
(4) The keyboard according to the present invention is provided with at least two or more of the key switch devices according to the first invention, the second invention, or the third invention. The keyboard of the present invention being provided with the key switch device according to the first, second, or third invention can provide the same effects as those described about the first, second, and third inventions.
(5) The electronic device according to the present invention is characterized by including: a keyboard for inputting letters, symbols, and others, provided with a key switch device of the first invention including a key top and a pair of a first and a second link members movably disposed under the key top, for performing switching of a switching section while guiding a vertical movement of the key top by the first and second link members, the key switch including: a first cam portion formed in the first link member; a second cam portion formed in the second link member and disposed facing the first cam portion; a cantilever member formed in a cantilever beam shape extending from the first link member or the second link member to support at least one of the first cam portion and the second cam portion; and an urging member for elastically urging the cantilever member in which one of the cam portions is formed in a direction to bring the first cam portion and the second cam portion into contact with each other; display means for displaying the letters, symbols, and others; and control means for causing the display means to display the letter, symbols, and others based on the input data from the keyboard.
Furthermore, the electronic device according to the present invention is characterized by including: a keyboard for inputting letters, symbols, and others, provided with a key switch device of the second invention including a key top and a pair of a first and a second link members movably disposed under the key top, for performing switching of a switching section while guiding a vertical movement of the key top by the first and second link members, the key switch including: a first cam portion formed in the first link member; a second cam portion formed in the second link member and disposed facing the first cam portion; a first cantilever member formed in a cantilever beam shape extending from the first link member to support the first cam portion; a second cantilever member formed in a cantilever beam shape extending from the second link member to support the second cam portion; a first urging member for elastically urging the first cantilever member in a direction to bring the first cam portion and the second cam portion into contact with each other; and a second urging member for elastically urging the second cantilever member in a direction to bring the first cam portion and the second cam portion into contact with each other; display means for displaying the letters, symbols, and others; and
control means for causing the display means to display the letter, symbols, and others based on the input data from the keyboard.
Moreover, the electronic device according to the present invention is characterized by including a keyboard for inputting letters, symbols, and others, provided with a key switch device of the third invention including a key top and a pair of a first and a second link members movably disposed under the key top, for performing switching of a switching section while guiding a vertical movement of the key top by the first and second link members, the key switch including: a first cam portion formed in the first link member; a second cam portion formed in the second link member and disposed facing the first cam portion; a cantilever member formed in a cantilever beam shape extending from the first link member or the second link member to support at least one of the first cam portion and the second cam portion; and an urging member for elastically urging the cantilever member in which one of the cam portions is formed in a direction to bring the first cam portion and the second cam portion into contact with each other, wherein the first cam portion and the second cam portion are brought into contact with each other at contact portions, the first cam portion and the second cam portion each have a shape to cause the point of action of the urging force of the urging member acting on the contact portions to shift to a predetermined fixed point side of the urging member in association with a repeated switching operation; display means for displaying the letters, symbols, and others; and control means for causing the display means to display the letter, symbols, and others based on the input data from the keyboard.
In the electronic device on which the key switch device of the first invention is mounted, when letters, symbols, etc. are input through the key switch devices provided in the keyboard, the letters, symbols, etc. are displayed in the display means under control of the control means based on the input data from the keyboard. At this time, this electronic device is provided with the keyboard including the key switch device according to the first invention. As in the case with the key switch device of the first invention, one of the first cam portion of the first link member and the second cam portion of the second link member is supported by the cantilever member extending like a cantilever beam from the first or second link member and the urging member urges the cantilever member in the direction to bring the first and second cam portions into contact with each other. By the contact state of the first cam portion of the first link member and the second cam portion of the second link member and the cooperative operation of the urging member which urges the cantilever member, the key top is urged upward to be held in the non-depressed position and the key top can be returned to the non-depressed position upon cancellation of depression. Accordingly, the key switch device can be constructed without use of a rubber spring and a complicated urging mechanism, thus achieving a cost reduction. The urging member urges the cantilever member, so that the first and second cam portions are constantly held in contact with each other with the contact position varying in response to the vertical movement of the key top. By changing the shapes of the first and second cam portions as needed, therefore, it is possible to freely design the click touch which occurs during the key operation. Furthermore, the cantilever member is elastically urged by the urging member so that one of the first and second cam portions supported on the cantilever member is brought into contact with the other cam portion. The elastic force to bring the first and second cam portions into contact with each other may be produced by the urging member. Accordingly, the cantilever member is not requested to have the elastic force. Thus, the cantilever member can be made of a resinous material at low cost and to be relatively flexible. Consequently, there is little possibility that creep occurs in the cantilever member even when the switching operation is performed for a long term, and the switching operation can be ensured stably over a long term.
In the electronic device on which the key switch device of the second invention is mounted, when letters, symbols, etc. are input through the key switch devices provided in the keyboard, the letters, symbols, etc. are displayed in the display means under control of the control means based on the input data from the keyboard. At this time, this electronic device is provided with the keyboard including the key switch device according to the second invention. As in the case with the key switch device of the second invention, the first cantilever member supporting the first cam portion of the first link member is urged by the first urging member and the second cantilever member supporting the second cam portion of the second link member is urged by the second urging member, respectively, in a direction to bring the first and second cam portions into contact with each other. Accordingly, by the contact state of the first and second cam portions and the cooperative operation of the first and second urging members which urge the first and second cantilever members respectively, the key top is urged upward to be held in the non-depressed position and the key top can be returned to the non-depressed position upon cancellation of depression. Accordingly, the key switch device can be constructed without use of a rubber spring and a complicated urging mechanism, thus achieving a cost reduction. The first and second urging members urge the first and second cantilever members, so that the first and second cam portions are constantly held in contact with each other with the contact position varying in response to the vertical movement of the key top. By changing the shapes of the first and second cam portions as needed, therefore, it is possible to freely design the click touch which occurs during the key operation. Furthermore, the first and second cantilever members are elastically urged by the first and second urging members so that the first and second cam portions supported on the cantilever members are brought into contact with each other. The elastic force to bring the first and second cam portions into contact with each other may be produced by the first and second urging members. Accordingly, the first and second cantilever members are not requested to have the elastic force. Thus, each cantilever member can be made of a resinous material at low cost and to be relatively flexible. Consequently, there is little possibility that creep occurs in each cantilever member even when the switching operation is performed for a long term, and the switching operation can be ensured stably over a long term.
Moreover, in the electronic device on which the key switch device of the third invention is mounted, when letters, symbols, etc. are input through the key switch devices provided in the keyboard, the letters, symbols, etc. are displayed in the display means under control of the control means based on the input data from the keyboard. At this time, this electronic device is provided with the keyboard including the key switch device according to the third invention. As in the case with the key switch device of the third invention, one of the first cam portion of the first link member and the second cam portion of the second link member is supported by the cantilever member extending like a cantilever beam from the first or second link member and the urging member urges the cantilever member in the direction to bring the first and second cam portions into contact with each other. By the contact state of the first cam portion of the first link member and the second cam portion of the second link member and the cooperative operation of the urging member which urges the cantilever member, the key top is urged upward to be held in the non-depressed position and the key top can be returned to the non-depressed position upon cancellation of depression. Accordingly, the key switch device can be constructed without use of a rubber spring and a complicated urging mechanism, thus achieving a cost reduction. The urging member urges the cantilever member, so that the first and second cam portions are constantly held in contact with each other with the contact position varying in response to the vertical movement of the key top. By changing the shapes of the first and second cam portions as needed, therefore, it is possible to freely design the click touch which occurs during the key operation. Furthermore, the cantilever member is elastically urged by the urging member so that one of the first and second cam portions supported on the cantilever member is brought into contact with the other cam portion. The elastic force to bring the first and second cam portions into contact with each other is produced based on the elastic force of the cantilever member and the elastic force of the urging member. At this time, the contact portions of the first and second cam portions may wear due to the repeated switching operation at the switching section based on the depression operation of the key top, which reduces the initial urging force to be exerted on the cantilever member through the urging member. The first and second cam portions each have the shape to cause the point of action of the urging force acting on the contact portions of the first and second cam portions to shift to a predetermined fixed point side of the urging member. In the case where the contact portions wear, the point of action of the urging force comes close to the fixed point side of the urging member, increasing the urging force to be exerted on the cantilever member through the urging member. Thus, the reduction in the initial urging force of the urging member due to wear of the contact portions of the first and second cam portions is cancelled out by an increment of the increased urging force when the point of action of the urging force in the contact portions comes close to the fixed point side of the urging member. Consequently, even if the switching operation is repeatedly performed for a long term, the depression characteristic of the key top can be surely prevented from being largely changed and can be stabilized. The switching operation can be ensured stably over a long term. In the case where the elastic force of the cantilever member is reduced due to the repeated switching operation, similarly, the action point of the urging force of the urging member in the contact portions of the first and second cam portions comes close to the fixed point side of the urging member as mentioned above, which increases the urging force to be exerted on the cantilever member through the urging member. Accordingly, the increased urging force can compensate the reduction in the elastic force of the cantilever member. This also makes it possible to stabilize the depression characteristic of the key top.